U.S. crude stocks rose by 3.7 million barrels in the week to Aug. 10, to 410.8 million barrels, private industry group the American Petroleum Institute (API) said on Tuesday. Crude stocks at the Cushing, Oklahoma, delivery hub rose by 1.6 million barrels, the API said.

Official U.S. fuel inventory data is due to be published later on Wednesday by the Energy Information Administration.

Sentiment was also clouded by a darkening economic outlook which could start impacting oil demand, traders said.

The OECD’s composite leading indicator, which covers the western advanced economies plus China, India, Russia, Brazil, Indonesia and South Africa, peaked in January but has since fallen and slipped below trend in May and June.

World trade volume growth also peaked in January at almost 5.7 percent year-on-year, but nearly halved to less than 3 percent by May, according to the Netherlands Bureau for Economic Policy Analysis.

BMI Research said oil markets would “struggle for direction, as uncertainty around both the impact on supply from the Iranian sanctions and escalating trade tensions between the U.S. and China persists.”